1. Field of the Invention
The present invention relates to a white light emitting diode, and more particularly, to a white light emitting diode, wherein a molding member with a red fluorescent substance mixed therein is formed on a blue light emitting diode chip and a green light emitting diode chip.
2. Description of the Related Art
As red, orange, green, blue and white light emitting diodes with high luminance have recently appeared with the development of compound semiconductor technology, light emitting diodes, which were mainly used for simple indicators, dial plates and the like in the prior art, have been applicable to a variety of fields in which full colors, high reliability, low power consumption and miniaturization are required. In particular, as the illumination efficiency of a white light emitting diode is superior to that of an incandescent bulb, the appearance of the white light emitting diode shows possibility of use as an illumination light source, and the white light emitting diode has been also used as a backlight source of a liquid crystal display (LCD). There have been developed a variety of methods for implementing such white light emitting diodes, which include a method of obtaining white light by coupling a fluorescent substance on a blue or ultraviolet light emitting diode chip as a single chip type, a method of obtaining white light by combining two or three light emitting diodes as a multi-chip type, and the like.
Among conventional techniques, in a case where a blue light emitting diode is used, the blue light emitting diode is used as an excitation light source and excited light is passed through a fluorescent substance of YAC (Yttrium Aluminum Garnet) emitting yellow light so as to implement a white light emitting diode. However, this method has disadvantages in that a flicker effect frequently occurs due to color separation resulting from a wide wavelength interval between blue and yellow light, and it is difficult to control color temperature and a color rendering evaluation index. Further, there is a method of implementing a white light emitting diode by applying red, green and blue fluorescent substances on an ultraviolet light emitting diode chip. However, there is a problem in that the ultraviolet light emitting diode chip has a short life span and low efficiency.
Meanwhile, although red, green and blue light emitting diode chips are combined to implement a white light emitting diode with multi-chips, there is a problem in that the operation voltage of each of the chips is not uniform, and the output of each of the chips varies depending on an ambient temperature.
FIGS. 1A and 1B are perspective and sectional views of a white light emitting diode according to a prior art. Referring to FIGS. 1A and 1B, there is shown a case where a blue light emitting diode is used as an excitation light source and excited light is passed through a fluorescent substance of YAG (Yttrium Aluminum Garnet) emitting yellow light so as to implement a white light emitting diode. The white light emitting diode shown in FIGS. 1A and 1B is a side view type fight emitting diode used as a backlight source of an LCD. The white light emitting diode comprises a substrate 110, a first lead terminal 120, a second lead terminal 130, a blue light emitting diode chip 140, a reflection portion 150, a wire 160, a fluorescent substance 170 and a molding member 180.
In the side view type white light emitting diode, the first lead terminal 120 and the second lead terminal 130 are arranged on the substrate 110, and the blue light emitting diode chip 140 is mounted on the second lead terminal 130. The reflection portion 150 for laterally reflecting light emitted from the blue light emitting diode chip 140 is formed on the substrate 110, the molding member 180 encapsulates the blue light emitting diode chip 140, and the fluorescent substance 170, e.g., YAG (Yttrium Aluminum Garnet) is mixed in the molding member 180. As a result, blue light emitted from the blue light emitting diode chip 140 excites the fluorescent substance 170 to generate yellow light, and white light is emitted due to constructive interference of the yellow light and the blue light. Thus, since only the blue light and the yellow light exist, there is limitation on expression of red and green, which causes a problem of deterioration of color reproducibility. Further, as described above, since white light emitting diodes implemented according to the prior art have problems, there is a current need for white light emitting diodes that solve these problems.